.shoucang{
    width: 100%;
    .nav{
        position: absolute;
        top: 50%;
        left: 50%;
        display: flex;
        align-items: center;
        justify-content: center;
        width: 150px;
        height: 150px;
        margin-top: -75px;
        margin-left: -75px;
        background: white;
        border-radius: 16px;
    }
}